‘Fundamental failures’ were made by the Home Office when they housed asylum seekers in military barracks in Wales and England, an inspectors report has found.
Two watchdogs inspected conditions at Penally Camp in Pembrokeshire and Napier Barracks in Kent, and key findings were published last month.
However, a full report, released on Thursday, has laid bare the extent of the concerns raised.
Both sites have been used to accommodate hundreds of asylum seekers since September, despite repeated warnings they were unsuitable.
The report from the Independent Chief Inspector of Borders and Immigration (ICIBI) and Her Majesty's Inspectorate of Prisons (HMIP) was released on Thursday after the PA news agency made requests to obtain the document during a two-day court hearing.
It said: "There were fundamental failures of leadership and planning by the Home Office, which had led to dangerous shortcomings in the nature of the accommodation and poor experiences for the residents".
Staff from the department "were rarely present at either site" and managers at both sites lacked "the experience and skills to run large-scale communal accommodation." it added.
The inspections found that both camps were "impoverished, run-down and unsuitable for long-term accommodation".
At one point, 171 asylum seekers were being housed in Penally, which made the site "cramped" and "effective social distancing difficult".
It also said some areas were "filthy", and that the vast majority of people in Penally said they had felt depressed at some points.
Inspectors said: "They had little to do to fill their time, a lack of privacy, a lack of control over their day-to-day lives, and limited information about what would happen to them.
"These factors have had a corrosive effect on residents' morale and mental health."
Concerns were also raised by both Public Health Wales and Public Health England about the Covid-19 safety of both sites.
At Napier Barracks, almost 200 people tested positive for coronavirus during an outbreak in January and February.
Both sites were opened before recommendations were implemented.
The inspectors said: "Given the cramped communal conditions and unworkable cohorting at Napier, once one person was infected a large-scale outbreak was virtually inevitable."
On March 16th it was confirmed that all asylum seekers would be moved out of Penally Camp by the end of the month.
The decision was said to be made after "many weeks of discussions" with the Home Office.
Home Secretary Priti Patel and immigration minister Chris Philp have both previously defended the use of the sites.
In a letter to residents from Welsh Secretary Simon Hart, The Home Office said they recognised that the use of Penally Camp contributed to heightened tensions, but stressed "they had little option at the time."